Join the #1 community for gun owners of the Northwest
We believe the 2nd Amendment is best defended through grass-roots organization, education, and advocacy centered around individual gun owners. It is our mission to encourage, organize, and support these efforts throughout Oregon, Washington, Idaho, Montana, and Wyoming.
Discuss firearms and all aspects of firearm ownership
Join others in organizing against anti-gun legislation
Find nearby gun shops, ranges, training, and other resources
Discover free outdoor shooting areas
Stay up to date on firearm-related events
Share photos and video with other members
...and much more!
compact
In mathematics, specifically general topology, compactness is a property that generalizes the notion of a subset of Euclidean space being closed (containing all its limit points) and bounded (having all its points lie within some fixed distance of each other).
Examples of compact spaces include a closed real interval, a union of a finite number of closed intervals, a rectangle, or a finite set of points. This notion is defined for more general topological spaces in various ways, which are usually equivalent in Euclidean space but may be inequivalent in other spaces.
One such generalization is that a topological space is sequentially compact if every infinite sequence of points sampled from the space has an infinite subsequence that converges to some point of the space.
The Bolzano–Weierstrass theorem states that a subset of Euclidean space is compact in this sequential sense if and only if it is closed and bounded.
Thus, if one chooses an infinite number of points in the closed unit interval [0, 1], some of those points will get arbitrarily close to some real number in that space.
For instance, some of the numbers in the sequence 1/2, 4/5, 1/3, 5/6, 1/4, 6/7, … accumulate to 0 (while others accumulate to 1).
The same set of points would not accumulate to any point of the open unit interval (0, 1), so the open unit interval is not compact. Although subsets (subspaces) of Euclidean space can be compact, the entire space itself is not compact since it is not bounded.
For example, considering
R
1
{\displaystyle \mathbb {R} ^{1}}
, the entire real number line, the sequence of points 0, 1, 2, 3, …, has no subsequence that converges to any real number.
Compactness was formally introduced by Maurice Fréchet in 1906 to generalize the Bolzano–Weierstrass theorem from spaces of geometrical points to spaces of functions. Arzelà–Ascoli theorem and the Peano existence theorem exemplify applications of this notion of compactness to classical analysis. Following its initial introduction, various equivalent notions of compactness, including sequential compactness and limit point compactness, were developed in general metric spaces. In general topological spaces, however, these notions of compactness are not necessarily equivalent. The most useful notion—and the standard definition of the unqualified term compactness—is phrased in terms of the existence of finite families of open sets that "cover" the space in the sense that each point of the space lies in some set contained in the family. This more subtle notion, introduced by Pavel Alexandrov and Pavel Urysohn in 1929, exhibits compact spaces as generalizations of finite sets. In spaces that are compact in this sense, it is often possible to patch together information that holds locally—that is, in a neighborhood of each point—into corresponding statements that hold throughout the space, and many theorems are of this character.
The term compact set is sometimes used as a synonym for compact space, but often refers to a compact subspace of a topological space as well.
For Sale is a New in the Box S&W M&P9 compact in 9mm. This has a 4” barrel and was mfg in 2021. Optic ready, Apex threaded barrel, box, paperwork, (3)-15rd mags and back straps. Also has suppressor sights and comes with factory 4” barrel. Also can come with Trijicon RMR Red Dot Type 2 3.25...
Looking to see if anybody is selling USPC 9 mags, has a nice HK USP compact 9mm Holster or other accessories for the USP compact 9mm send me a message with what you have and your price.
Hello,
I have a CZ P01 Omega in great condition that I would like to trade for a Beretta PX4 Compact or Compact Carry.
The P01 is in great condition and has the MCarbo trigger upgrade.
I am looking for the PX4 Compact Carry (the Langdon Tactical version.) plus some money on my end.
Trades...
Picked this up as an understudy to my Shield but I haven't ended up shooting it that much 🤷♂️
I got it used so no idea on round count, I have heard that some of them preferer HV ammo but I took it out the other day and ran 2 mags each of CCI SV and Federal Champion and it ran fine :)
Comes...
I am looking to see if anybody is selling a USP compact 9mm locally looking to spend around $900 cash ready please message me directly looking to buy to tomorrow. If I can’t find one locally I’ll order online. If you’re looking to off load a USP compact 9mm before 114 goes back to court let me...
For sale or trade is a cz75 pcr compact with a black arch protos iwb holster and 6 15rd magazines. It also has a pair of g10 grips that are not installed at the moment with the original grips currently on it. I've only had this combo for a couple months but I've decided I need something even...
S&W M&P M2.0 Compact 4" for sale.
Has a red fiber optic front sight post.
Comes with 2 15-round magazines.
Comes with an Alien Gear Rapid Force Duty Holster and a Safariland 6360RDS with GhostMen Designs Portal and ALS Nub Mod modifications.
Carried by my wife for armed security. Less than...
Selling my CZ 75 compact with a Cajun gunworks pro kit (formally defensive carry kit) Also comes with a stainless guide rod and night sights.
I bought the gun used. Iv put around 120 or so round through it. Very accurate and not a single hiccup.
Selling because I have another CZ 75 compact I...
P320 9mm complete slide assembly, barrel & recoil assembly with low round count. Factory night sights are in great shape. 3.9” barrel
This will fit your compact P320 grip module.
Will not work with the smaller sub compact 3.6” version or the 4.7” full size P320.
This is not the optic cut...
Brand new in package Sig P320 compact threaded barrel. 1/2x 28 threads for most all compensators and suppressors.
I’m willing to ship, buyer pays for shipping.
Hi all,
I've been looking into picking up a PSA dagger (saw a good deal on PSA for two frames). Wanted to ask if anyone here owns and has shot their Dagger and what they think of it. The compact will likely become a carry pistol. Any issues with reliability? How's the accuracy? Any other...
I bought the gun for a backup for hunting went to change sights out and busted the front sight.
Guns basically brand new. Has has 10 rounds though her.
I don't know where the original case is and don't know what happened to the magwell.
And I lost the replacement front sight.
Long story...
Selling/trading my sig p320 compact pistol. This started as an FCU I picked up in a trade. The spring, upper, grip and 2x15 round mags came off a pistol I bought. The gold barrel is aftermarket. I can’t remember which brand. It has not been used. The fcu has been used in another gun. Everything...
Solid and compact 9mm, great EDC size without the snappiness of the micro-compacts. Fabulous firearm for the money, great condition, just have too many polymer 9mm's. It's been upgraded with front & rear XS tritium night sights, otherwise fully stock. Includes factory box, 3 mags (15rd x2 + 17rd...
For sale:
Glock 23 Gen 5 .40 S&W, with Trijicon HD night sights, six magazines, and all factory accessories. Less than 200 rounds fired. $420.
Smith and Wesson M&P40 2.0 Compact, 4-inch barrel, with seven magazines, and Ameriglo I-Dot night sights. Fewer than 300 rounds fired. Also with all...